This invention relates to screens for separating solid particles from fluids or fluid slurries. In one of its aspects this invention relates to coatings for separating screens. In another of its aspects this invention relates to the separation of "gummy" material and larger solid particles from a fluid stream.
In one of its concepts this invention relates to the method of separation of larger solid particles and gummy material from circulating drilling mud by a separator screen coated with a coating to which the gummy material does not easily adhere, thereby allowing the gummy material to pass across the screen with the larger solid particles.
The art of separating solid particles from fluid streams by passing a fluid through a screening device having perforations of such size that solid particles are retained on the screen surface instead of passing through is well known. In some processes it is not simply a matter of passing solid particles carried in a fluid stream across a screening device to obtain a separation. Some fluid streams contain additional materials that cause solid particles to adhere to each other or to the screen surface ultimately bridging the openings in the screen and blinding the screen surface. Such a problem is frequently encountered in the drilling of wells during which operation a drilling mud is circulated into the drill hole. The mud carries drilling cuttings back to the surface where the cuttings are separated from the drilling mud before the mud is recirculated to the drilling operation.
Frequently in drilling operations a gummy clay formation is encountered which makes the separation of drilling cuttings from the drilling liquid by screening operations very difficult. The gummy clay, sometimes called gumbo, adheres to metal surfaces causing a buildup on the metal screen which can blind the screens so that fluid material for separation passes over the screen side instead of through the screen. I have discovered that coating a metal screen, including both the perforated surface and the screen support, with a polymeric substance that forms a "slick" surface alleviates the problems sufficiently to prevent the blinding of the screen and the consequential overflow of the screen.
It is therefore an object of this invention to provide an efficient means for separating drilling solids and gummy mud from drilling liquids. It is another object of this invention to provide a shaker screen coated with polymeric coating of sufficient surface slickness to retard adherence of gummy substances to the screen.
Other aspects, objects and the advantages of this invention will be apparent to one skilled in the art upon studying the specification, drawing and the appended claims.